ProxyStructural.php: Приклад структури патерну

<?php
namespace RefactoringGuru\Proxy\Structural;
/**
* The Subject interface declares common operations for both RealSubject and the
* Proxy. As long as the client works with RealSubject using this interface,
* you'll be able to pass it a proxy instead of a real subject.
*/
interface Subject
{
public function request();
}
/**
* The RealSubject contains some core business logic. Usually, RealSubjects are
* capable of doing some useful work which may also be very slow or sensitive -
* e.g. correcting input data. A Proxy can solve these issues without any
* changes to the RealSubject's code.
*/
class RealSubject implements Subject
{
public function request()
{
print("RealSubject: Handling request.\n");
}
}
/**
* The Proxy has an interface identical to the RealSubject.
*/
class Proxy implements Subject
{
/**
* @var RealSubject
*/
private $realSubject;
/**
* The Proxy maintains a reference to an object of the RealSubject class. It
* can be either lazy-loaded or passed to the Proxy by the client.
*/
public function __construct(RealSubject $realSubject)
{
$this->realSubject = $realSubject;
}
/**
* The most common applications of the Proxy pattern are lazy loading,
* caching, controlling the access, logging, etc. A Proxy can perform one of
* these things and then, depending on the result, pass the execution to the
* same method in a linked RealSubject object.
*/
public function request()
{
if ($this->checkAccess()) {
$this->realSubject->request();
$this->logAccess();
}
}
private function checkAccess()
{
// Some real checks should go here. RU: Некоторые реальные проверки
// должны проходить здесь.
print("Proxy: Checking access prior to firing a real request.\n");
return true;
}
private function logAccess()
{
print("Proxy: Logging the time of request.\n");
}
}
/**
* The client code is supposed to work with all objects (both subjects and
* proxies) via the Subject interface in order to support both real subjects and
* proxies. In real life, however, clients mostly work with their real subjects
* directly. In this case, to implement the pattern more easily, you can extend
* your proxy from the real subject's class.
*/
function clientCode(Subject $subject)
{
// ...
print($subject->request());
// ...
}
print("Client: Executing the client code with a real subject:\n");
$realSubject = new RealSubject();
clientCode($realSubject);
print("\n");
print("Client: Executing the same client code with a proxy:\n");
$proxy = new Proxy($realSubject);
clientCode($proxy);

Output.txt: Результат виконання

Client: Executing the client code with a real subject:
RealSubject: Handling request.
Client: Executing the same client code with a proxy:
Proxy: Checking access prior to firing a real request.
RealSubject: Handling request.
Proxy: Logging the time of request.

Приклад: Приклад з життя

ProxyRealWorld.php: Приклад з життя

<?php
namespace RefactoringGuru\Proxy\RealWorld;
/**
* Proxy Design Pattern
*
* Intent: Provide a surrogate or placeholder for another object to control
* access to the original object or to add other responsibilities.
*
* Example: There are countless ways proxies can be used: caching, logging,
* access control, delayed initialization, etc. This example demonstrates how
* the Proxy pattern can improve the performance of a downloader object by
* caching its results.
*/
/**
* The Subject interface describes the interface of a real object.
*
* The truth is that many real apps may not have this interface clearly defined.
* If you're in that boat, your best bet would be to extend the Proxy from one
* of your existing application classes. If that's awkward, then extracting a
* proper interface should be your first step.
*/
interface Downloader
{
public function download(string $url): string;
}
/**
* The Real Subject does the real job, albeit not in the most efficient way.
* When a client tries to download the same file for the second time, our
* downloader does just that, instead of fetching the result from cache.
*/
class SimpleDownloader implements Downloader
{
public function download(string $url): string
{
print("Downloading a file from the Internet.\n");
$result = file_get_contents($url);
print("Downloaded bytes: " . strlen($result) . "\n");
return $result;
}
}
/**
* The Proxy class is our attempt to make the download more efficient. It wraps
* the real downloader object and delegates it the first download calls. The
* result is then cached, making subsequent calls return an existing file
* instead of downloading it again.
*
* Note that the Proxy MUST implement the same interface as the Real Subject.
*/
class CachingDownloader implements Downloader
{
/**
* @var SimpleDownloader
*/
private $downloader;
/**
* @var string[]
*/
private $cache = [];
public function __construct(SimpleDownloader $downloader)
{
$this->downloader = $downloader;
}
public function download(string $url): string
{
if (!isset($this->cache[$url])) {
print("CacheProxy MISS. ");
$result = $this->downloader->download($url);
$this->cache[$url] = $result;
} else {
print("CacheProxy HIT. Retrieving result from cache.\n");
}
return $this->cache[$url];
}
}
/**
* The client code may issue several similar download requests. In this case,
* the caching proxy saves time and traffic by serving results from cache.
*
* The client is unaware that it works with a proxy because it works with
* downloaders via the abstract interface.
*/
function clientCode(Downloader $subject)
{
// ...
$result = $subject->download("http://example.com/");
// Duplicate download requests could be cached for a speed gain.
$result = $subject->download("http://example.com/");
// ...
}
print("Executing client code with real subject:\n");
$realSubject = new SimpleDownloader();
clientCode($realSubject);
print("\n");
print("Executing the same client code with a proxy:\n");
$proxy = new CachingDownloader($realSubject);
clientCode($proxy);

Output.txt: Результат виконання

Executing client code with real subject:
Downloading a file from the Internet.
Downloaded bytes: 1270
Downloading a file from the Internet.
Downloaded bytes: 1270
Executing the same client code with a proxy:
CacheProxy MISS. Downloading a file from the Internet.
Downloaded bytes: 1270
CacheProxy HIT. Retrieving result from cache.